1. Field of the Invention
The present invention relates to the decoupling of the aiming of the beam of an electronic scanning antenna from the motions of the moving body that supports it, whether the aiming of the beam is done by scanning during a watch or by the following of angular deviation measurement signals in target-tracking mode. It also relates to the guidance of a moving body fitted out with an electronic scanning antenna radar in order to track a target followed by means of angular deviation measurement signals delivered by the electronic scanning antenna.
2. Description of the Prior Art
There are known ways of decoupling the aiming of an antenna that is mechanically steerable in elevation and in azimuth from the motion of its supporting platform. A standard way of achieving this consists in equipping the antenna with gyroscopic mechanisms which, through a servocontrol system, prevent it from following the rotational motions of its support. However, mechanisms such as these are bulky and cumbersome, and it is therefore sought to eliminate them.
Another method to decouple the aiming of a mechanically steerable antenna from the motions of its support consists in using the indications given by an inertial unit linked to the support to eliminate the effects of the motion of the support on the aiming of the antenna by means of two servocontrol systems controlling the elevation and azimuth angles of aim of the antennas. It is then necessary, by means of trigonometrical relationships, to express the components of the inherent speed of rotation of the support given by the inertial unit with respect to a frame of reference or referential frame related to the support, in terms of variations of elevation and azimuth angles.
It has been proposed, notably by the U.S. patent application No. 5,052,637, to apply the latter decoupling method to electronic scanning antennas even though they are rigidly fixed to their support and even though the elevation and azimuth angles are not the variables used in electronic aiming. This results in complications in the computations that could lead to harmful couplings.